Listing of bad valve batch numbers anyehere?

2007 made Marshall 2266. Someone had been in there before and changed ECC83 V3 and V4 which function and tested fine. Impossible valve crackle V1 and V2 are probably originals , at least 07 dates agree V2 had a tested CH/R of 700K marked VLVE 0066 and grey shields dated 02/07 V1 marginally acceptable (part of the valve sound) noise intrusion VLVE 0067 and shiney shields, dated 04/07 with a tested CHR of 15M. Now both measure 25M or better, driving heaters to 13V for a couple of seconds and placed in my emergency- use pile of similar questionables Is this just random failures or are there know bad batches listed somewhere.?

From an amp retailer insider source BlackStar amps have been hit by complete batches of amps with bad valves, did they take the same valve supplier they were used to at Marshall? In valve production is a routine final stage , over-driving the heaters to push back the oxide coatings of the heaters , if they happen to be marginal clearance. I know this fudge , like for the 700K one above is only temporary in that it will return after a few hundred hours of normal use, without vibration/abuse

Reply to
N_Cook
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"Nutcase Kook"

** LOL.

Would that be the ECC81s they use for OUTPUT valves in their mini amps ?

No kidding, the two halves operate in class A push-pull ( 300VDC supply) and deliver about 0.5 W into an 8 ohm speaker.

But not for long ................

** The "supplier " is not too relevant.

AFAIK China only has one factory making audio valves.

... Phil

Reply to
Phil Allison

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